MySQL count N consecutive days in normal form tables - mysql

Question

I want to count N consecutive days that a specific user has meetings, on a given date and before it.
For example: count the consecutive meeting days that a user with id 1 has at 16 January 2013.
I found some good answers here and here but the tables are not in normal form like my sample above and i cannot figure out how to implement it for my occasion.
A sample table structure as follows:
CREATE TABLE IF NOT EXISTS `meetings` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`time` datetime NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE IF NOT EXISTS `meetings_users` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`user_id` int(10) unsigned NOT NULL,
`meeting_id` int(10) unsigned NOT NULL,
PRIMARY KEY (`id`),
KEY `user_id` (`user_id`),
KEY `meeting_id` (`meeting_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE IF NOT EXISTS `users` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
--
-- Constraints for table `meetings_users`
--
ALTER TABLE `meetings_users`
ADD CONSTRAINT `meetings_users_ibfk_2` FOREIGN KEY (`meeting_id`) REFERENCES `meetings` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
ADD CONSTRAINT `meetings_users_ibfk_1` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE CASCADE ON UPDATE CASCADE;
Sample inserts
INSERT INTO `users` ( `id` ) VALUES (1)
INSERT INTO `meetings` ( `id`, `time` ) VALUES
(1, '2013-01-14 10:00:00'),
(2, '2013-01-15 10:00:00'),
(3, '2013-01-16 10:00:00')
INSERT INTO `meetings_users` ( `id`, `meeting_id`, `user_id` ) VALUES
(1, 1, 1),
(2, 2, 1),
(3, 3, 1)
Desired output:
*+---------+-----------------+
| user_id | consecutive_days |
+---------+------------------+
| 1 | 3 |
+---------+------------------+

Answer 1

How about something like this. I expect it can be re-written without the subqueries but I must be having a bit of a brain freeze... (data set and query amended to suit shifting requirements)
DROP TABLE IF EXISTS meetings;
CREATE TABLE IF NOT EXISTS meetings
( meeting_id int(10) unsigned NOT NULL AUTO_INCREMENT
, meeting_time datetime NOT NULL
, PRIMARY KEY (meeting_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS meetings_users;
CREATE TABLE IF NOT EXISTS meetings_users
( user_id int(10) unsigned NOT NULL
, meeting_id int(10) unsigned NOT NULL
, PRIMARY KEY (meeting_id,user_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS users;
CREATE TABLE IF NOT EXISTS users
( user_id int(10) unsigned NOT NULL AUTO_INCREMENT
, PRIMARY KEY (user_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO users ( user_id ) VALUES (1),(2),(3),(4);
INSERT INTO meetings ( meeting_id, meeting_time ) VALUES
(1, '2013-01-14 10:00:00'),
(2, '2013-01-15 10:00:00'),
(3, '2013-01-16 10:00:00'),
(4, '2013-01-17 10:00:00'),
(5, '2013-01-18 10:00:00'),
(6, '2013-01-19 10:00:00'),
(7, '2013-01-20 10:00:00'),
(8, '2013-01-14 12:00:00');
INSERT INTO meetings_users (meeting_id, user_id ) VALUES
(1, 1),
(2, 1),
(2, 3),
(3, 1),
(3, 3),
(4, 2),
(4, 3),
(5, 2),
(6, 1),
(1, 8);
SET #dt = '2013-01-15';
SELECT user_id
, start
, DATEDIFF(#dt,start)+1 cons
FROM
(
SELECT a.user_id
, a.meeting_date Start
, MIN(c.meeting_date) End
, DATEDIFF(MIN(c.meeting_date),a.meeting_date) + 1 diff
FROM (SELECT DISTINCT mu.user_id,DATE(m.meeting_time) meeting_date FROM meetings_users mu JOIN meetings m ON m.meeting_id = mu.meeting_id) a
LEFT
JOIN (SELECT DISTINCT mu.user_id,DATE(m.meeting_time) meeting_date FROM meetings_users mu JOIN meetings m ON m.meeting_id = mu.meeting_id) b
ON b.user_id = a.user_id
AND a.meeting_date = b.meeting_date + INTERVAL 1 DAY
LEFT
JOIN (SELECT DISTINCT mu.user_id,DATE(m.meeting_time) meeting_date FROM meetings_users mu JOIN meetings m ON m.meeting_id = mu.meeting_id) c
ON c.user_id = a.user_id
AND a.meeting_date <= c.meeting_date
LEFT
JOIN (SELECT DISTINCT mu.user_id,DATE(m.meeting_time) meeting_date FROM meetings_users mu JOIN meetings m ON m.meeting_id = mu.meeting_id) d
ON d.user_id = a.user_id
AND c.meeting_date = d.meeting_date - INTERVAL 1 DAY
WHERE b.meeting_date IS NULL
AND c.meeting_date IS NOT NULL
AND d.meeting_date IS NULL
GROUP
BY a.user_id
, a.meeting_date
) x
WHERE #dt BETWEEN start AND end;
+---------+------------+------+
| user_id | start | cons |
+---------+------------+------+
| 1 | 2013-01-14 | 2 |
| 3 | 2013-01-15 | 1 |
+---------+------------+------+